Varieties of Democracy (V-DEM) Project (link)
Democracy along multiple dimensions. Scores are determined by:
Polling a large group of area experts on a range of democratic dimensions (electoral, deliberative, liberal etc.)
Using an algorithm to aggregate those responses into scores along each dimension.
Both of these approaches have acknowledged trade-offs. The minimalist view has the advantage of parsimony, but the more nuanced measures may get us closer to the ideal conceptual definition.
But neither is free from error.
Also note, these are influenced by different conceptual definitions, which are in turn potentially influenced by some normative considerations.